Difficulties can occur in the yarn supply in two-for-one twisting spindles or in bobbin creels if threads are drawn off from at least two feed bobbins, which are slipped one on top of the other, and are fed to the machining device. For example, yarns are drawn off from two single-winding cross-wound bobbins, which are slipped one on top of the other and are fed, for example, to the yarn inlet tube of a two-for-one twisting spindle. A brake ring or floating ring, which is disclosed in German Patent Specification No. 563 593 and which is slipped onto the yarn inlet tube, can be used for such a yarn supply. This brake ring or floating ring is a simple, smooth ring beneath which either the yarns from the two feed bobbins, or the top yarn only, are guided on the way to the top of the yarn inlet tube, so that the brake ring is lifted by the yarns entering the spindle such that it is suspended and its weight tensions the yarn.
The yarn entry of two yarns, taken for example from single-winding cross-wound bobbins, does not correspond to the yarn entry of a doubled yarn, which enters the area of the brake ring or floating ring as a single yarn and lifts the ring in a defined manner at one point.
The two yarns coming from single-winding cross-wound bobbins are independent of one another and enter the brake ring zone with different yarn tensions. This can be caused, for example, by the different diameters of the two run-off or feed bobbins. Irregular yarn entry may also be caused by the taper of the bobbin or by the crossing angle. When two or more separate yarns enter the zone of the brake ring, the yarn with the higher entry tension will lift the brake ring or floating ring. A gap is thus formed on a section between the brake and its bearing face, which gap is larger than the average gap dependent upon the yarn thickness. The second yarn may, by chance, enter the resulting space or gap and is thus not braked like the yarn having the higher entry tension, which has lifted the brake ring.
As a result, a loop may be formed, particularly in the case of high-twist spun yarn.
In order to obtain uniform braking of the individual yarns, which enter independently from one another, without the yarns affecting one another, and to even out the tensions of the individually supplied yarns, a braking device, which is described in German Patent Specification No 31 24 482 corresponding to U.S. Pat. No. 4,434,609, and which is for use in a two-for-one twisting spindle and has a slip-on member and a brake ring mounted thereon, is designed in such a way that the brake ring is provided in the manner of a comb with teeth, which extend inwardly and obliquely upwardly and are inclined in the same direction in the peripheral direction of the delivered yarns, at least two of which overlap along each generatrix line of the slip-on member, wherein the part of the slip-on member accommodating the brake ring is conical and the upper side of the slip-on member is defined by an annular shoulder which projects radially outwardly and has a rounded edge, thereby forming a groove.
By using a comb-like ring as a braking member, which is known from other textile machines, in conjunction with a specially formed counter-member or slip-on member, the individual yarns are braked without the tension of one yarn influencing the tension of the other yarn during the braking operation.
It is the object of the invention to design a braking device, in particular for a two-for-one twisting spindle, in which at least two yarns are drawn off simultaneously and separately from one another from at least two feed bobbins, in such a way that the independently supplied individual yarns are braked evenly, without being affected by another yarn, in order to achieve an evening out of the yarn tensions of the individual yarns without using a comb-like brake ring.
This object is achieved by an improved yarn brake mechanism including a slip-on member including bearing means for being rotatably mounted on the upper end portion of the yarn inlet tube for rotation relative thereto. The slip-on member comprises a rotationally symmetrical member having a necked-down portion. A brake ring is floatingly received and mounted in the necked-down portion on the slip-on member and receives the separate yarns between the brake ring and the slip-on member as the yarns move from the supply packages to the yarn inlet tube for applying desired tension to the yarns. As a result of the rotation of the slip-on member caused by the friction forces of the yarn, the rotational speed of the slip-on member is commensurate with the rotational speed of the yarns being delivered by the bobbin, which ensures that the yarns are handled carefully.
Slip-on members or inlet heads which are freely rotating and which are carried along by the yarn are already known, for example from German Patent Specification No. 1 170 290. This entry head has, however, at least one yarn guide slot, so that it is not possible for the yarn to slide in the peripheral direction of the inlet head. However, such enforced guiding of a yarn is not admissible when two yarns, which are delivered from two feed bobbins, are supplied separately.